We misunderstand the motivations of the bully. We assume he (or she, but let's go with he) delights in his sheer will-to-dominate, that there is a feeling of power and concomitant jouissance (Hobbes's 'suddaine glory') in bullying others. But this is almost never the case. The vast majority of bullies feel themselves to be the ones picked upon, feel that they have been thwarted or treated unfairly, and bully others either in the service of some notion of equality of suffering, or justice, or in pursuit of some other motivation that dilutes what might otherwise be the bliss of the motiveless malignancy.
Take, for example, that subset of bullying we call racism. The racist does not soar freely in his own mind over the representative of the 'inferior' race; he already starts from a position where he is the one discriminated against, and acts with the belief that, should he ever be called to account his accusers will at least understand his mitigating circumstances. The fact that, actually, no such mitigating circumstances exist, that the victim of bullying neither knows nor ought to be care why the bully bullies, does not occur to the bully. Being a concentration camp guard feels to the guard like work, a chore, a duty, a self-sacrifice; and most racists and bullies feel the same way about their bullying. This is especially true of online bullying.